The disclosure herein relates generally to an imaging apparatus and fuser components thereof for use in electrostatographic, including digital, image-on-image, and like apparatuses. The fuser components, including fuser members, pressure members, donor members, external heat member, and the like, are useful for many purposes including fixing a toner image to a copy substrate. More specifically, the disclosure relates to fuser components comprising a fluorocarbon outer layer. In embodiments, the fluorocarbon outer layer is positioned on a substrate, which may be of many configurations including a roller, belt, film, or like substrate. In other embodiments, the fluorocarbon outer layer has an outer release layer thereon. In embodiments, there is positioned between the substrate and the outer fluorocarbon layer, an intermediate and/or adhesive layer. In embodiments, the fuser member outer coating comprises carbon black filler and has a conductivity within a specific range. The fuser member may be useful in xerographic machines, such as copiers, printers, facsimiles, multifunction machines, and including color machines.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles which are commonly referred to as toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support, which may be the photosensitive member itself, or other support sheet such as plain paper.
The use of thermal energy for fixing toner images onto a support member is well known and methods include providing the application of heat and pressure substantially concurrently by various means, a roll pair maintained in pressure contact, a belt member in pressure contact with a roll, a belt member in pressure contact with a heater, and the like. Heat may be applied by heating one or both of the rolls, plate members, or belt members. With a fixing apparatus using a thin film in pressure contact with a heater, the electric power consumption is small, and the warming-up period is significantly reduced or eliminated.
It is desired in the fusing process that minimal or no offset of the toner particles from the support to the fuser member take place during normal operations. Toner particles offset onto the fuser member may subsequently transfer to other parts of the machine or onto the support in subsequent copying cycles, thus increasing the background or interfering with the material being copied there. The referred to “hot offset” occurs when the temperature of the toner is increased to a point where the toner particles liquefy and a splitting of the molten toner takes place during the fusing operation with a portion remaining on the fuser member. The hot offset temperature or degradation of the hot offset temperature is a measure of the release property of the fuser, and accordingly it is desired to provide a fusing surface, which has a low surface energy to provide the necessary release. To ensure and maintain good release properties of the fuser, it has become customary to apply release agents to the fuser roll during the fusing operation. Typically, these materials are applied as thin films of, for example, silicone oils to prevent toner offset.
Another method for reducing offset is to impart antistatic and/or field assisted toner transfer properties to the fuser. However, to control the electrical conductivity of the release layer, the conformability and low surface energy properties of the release layer are often affected.
U.S. Pat. No. 6,419,615 discloses a fuser member having an outer layer of FEP with carbon black fillers dispersed therein.
U.S. Pat. No. 6,041,210 discloses a fuser member having PTFE and PFA, along with metal oxides dispersed therein, as an overcoat.
U.S. Pat. No. 6,159,588 discloses a fuser member having PTFE as an outer layer over a silicone rubber intermediate layer. The PTFE has alumina and silica particles dispersed therein.
U.S. Pat. No. 6,927,006 discloses a fuser member having an outer layer of PFA PTFE with carbon black over a silicone rubber intermediate layer. The patent discloses polyimide particles dispersed in the fluorocarbon outer layer.
Known fuser coatings include high temperature polymers such as polytetrafluoroethylene, perfluoroalkoxy, fluorinated ethylene propylene, silicone rubber, fluorosilicone rubber, fluoroelastomers, and the like. These coatings have been found to have adequate release properties and control toner offset sufficiently. However, these coatings do not tend to stay clean during use. Further, the coatings do not maintain a uniform surface. More specifically, the coatings often wear during use and/or become scratched during operation. In addition, these known surfaces often react with the toner and/or oil and/or debris from media, which causes the surface to become dirty and/or contaminated. The surface can, in turn, become physically damaged. The result of these problems is that the fuser member has a reduced useful function and short life. Another problem resulting from release coatings with high friction is unacceptable copy or print quality defects. The high friction often associated with conformable coatings may result in the generation of waves in the media being fused and/or the fuser member itself. This, in turn, results in copies or prints with localized areas of poorer fix and/or differential gloss.
Some of the above problems have been solved by recent improvements of adding polymer fillers to outer layers. However, the use of polymer fillers has caused other problems such as stripper finger marks present on copies, which leads to failure mode. Other failure modes include an offset failure mode problem. Further, wave defects have resulted.
Other problems results in that stripper fingers and charged paper or other input media, produce charge fringe fields on the fuser member surface. These charge fields then affect the un-fused toner image that is presented on the fuser roller. This, in turn, results in various image quality defects.
Therefore, a need remains for fuser components for use in electrostatographic machines that have superior electrical properties. More specifically, a need remains to decrease or eliminate the voltage differential and subsequent copy quality defect. The subtle voltage differences produced by: contacting members, substrate widths, or speed-related edge effects, results in image disturbances that are magnified after particle coalescence. These voltages, if not dissipated, exist for an indefinite period of time. The overall dissipation scheme involves a path from the conductive fuser member to the contacting conductive pressure member that is grounded via contact devices. A further need remains for fuser coatings having reduced susceptibility to contamination, scratching, and other damage. In addition, a need remains for fuser components having longer life. In addition, a need remains for fuser components with low friction while being resistant to scratching and other damage.